The quest got removed by AE in 2011. Which you still can check the quest, but you won't able to turn it in.
All of the rare quest got removed, which include all the rare Nulgath weapon.
It was actually available earlier this year for a few weeks. And then AE realized that they had accidentally put the quest back in-game after noticing turn-ins for the quest. Whenever you cheat, AE has a record of it. They can just decide when to swing the ban hammer though and ban everyone at once. XD